add a passive voice to an active form of the verb, NB: this construction is not replacing a subject with a pronoun, it is tacking on a pronoun (before the verb) to make the action a passive action by the subject.

si + 3rd person sing or plural of the verb, depending on the subject, if singular or plural, follow pattern of reflexive pronouns

passive voice without use of pronoun

essere + past participle (agree in gender and number with the subject to which it refers)